For certain applications it is required that a circuit breaker, after detecting a fault, opens the contacts and then quickly closes the contacts. When the fault remains, the contacts can then be kept open for a longer duration. The first opening and closing of the contacts should be performed in less than a second, typically less than 0.3 seconds. If the fault remains, the contacts can then be opened again and closed after a longer duration, for example a minute. This is called in the art an open-close-open (OCO) cycle.
Due to space restrictions in the switch gear, wherein the circuit breakers are applied, it is not possible to provide an electric motor, sufficient strong and quick to open and close the contacts within a split second. So, a mechanism is required in which for example spring energy is used to provide the quick opening and closing of the contacts.
U.S. Pat. No. 5,107,715 discloses a mechanism with open-close-open cycle for a circuit breaker. The circuit breaker is connected with a shaft which comprises a first, spring loaded, lever. The shaft is furthermore coupled via a freewheel coupling to a second shaft part on which a second, spring loaded, lever is arranged. When a fault occurs, the first lever is released driving the circuit breaker in an open position. Then the second lever is released driving the shaft further, such that the circuit breaker re-closes and the first spring is reloaded again. As the first lever is still released, the reloaded first spring will drive the shaft yet again further, such that the circuit breaker opens again.
This mechanism is quite complex and is voluminous. Furthermore, the reloading of the first spring depends on the spring force of the second spring, which thus needs to provide both the force to operate the circuit breakers and the force to reload the first spring.